This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-395296, filed Dec. 26, 2000; and No. 2001-347692, filed Nov. 13, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to a resistor for an electron gun assembly provided in a cathode-ray tube (CRT) apparatus, etc., and a method of manufacturing the resistor, and more particularly to a resistor for applying a resistor-divided voltage to an electrode provided in the electron gun assembly, and a method of manufacturing the resistor.
2. Description of the Related Art
Recently, a high voltage is required in a color cathode-ray tube apparatus in order to enhance the image quality. Accordingly, there is a possibility that a circuit element may be damaged by a spark current or discharge noise due to an intra-tube discharge. In this high-voltage use environment, a CRT apparatus includes a resistor for resistor-dividing a high voltage supplied to electrodes of an electron gun assembly to prevent the discharge and enhance the image quality.
Principal requirements for the resistor for the electron gun assembly are: 1) the resistor is stable in a breakdown voltage treatment or a heating step in a color CRT manufacturing process, 2) a variance in resistance and the amount of emission gas due to joule heat produced in operation are small, 3) the resistor does not become a secondary electron emission source when it is hit by dispersion electrons, and 4) the resistor does not disturb an electric field of the electron gun assembly, does not discharge, or does not displace the trajectory of electrons.
When specifications of the electron gun assembly are changed, the voltages to be supplied to respective electrodes of the electron gun assembly are varied in some cases. In this case, it is necessary to change a resistance division ratio in accordance with application voltages to the electrodes so as to supply optimal voltages to the electrodes in conformity to the changed specifications.
However, in the case of a resistor formed with a predetermined resistance division ratio, the resistance value of the resistor is adjustable only by a conventional trimming method. With the trimming method, the resistance value is only adjustable such that it is increased. In addition, in a resistor manufacturing process using screen printing, many resistors are formed at a time. To adjust the resistance value of each resistor by the trimming method will considerably decrease the manufacturing yield and is unfeasible.
Under the circumstances, when a resistance division ratio needs to be changed, a new resistor needs to be designed. A long time is required for completion of the design, evaluation, etc. of the new resistor. Consequently, the beginning of practical use of the new resistor will be delayed, and the beginning of practical use of the electron gun assembly and the CRT apparatus using the assembly will also be delayed.
The present invention has been made in consideration of the above problems, and an object of the invention is to provide a resistor for an electron gun assembly, which is easily provided with a predetermined resistance division ratio without lowering a manufacturing yield, a method of manufacturing the resistor, an electron gun assembly having the resistor, and a CRT apparatus having the resistor.
Another object of the invention is to provide a resistor for an electron gun assembly, which can prevent a decrease in manufacturing yield and the occurrence of a non-usable screen due to a shift of a division ratio caused by a variance among screens used in manufacture, a method of manufacturing the resistor, an electron gun assembly having the resistor, and a CRT apparatus having the resistor.
According to a first aspect of the invention, there is provided a resistor for an electron gun assembly, for applying a resistor-divided voltage to an electrode provided in the electron gun assembly, the resistor comprising: an insulative substrate; a plurality of first resistor elements disposed at predetermined positions on the insulative substrate; and a second resistor element having a predetermined pattern which electrically connects the first resistor elements, wherein the resistor has a structure in which an effective length of the second resistor element between the first resistor elements varies in accordance with a position of the second resistor element relative to the first resistor elements.
According to a second aspect of the invention, there is provided a method of manufacturing a resistor for an electron gun assembly, for applying a resistor-divided voltage to an electrode provided in the electron gun assembly, the method comprising: a step of forming a plurality of first resistor elements disposed at predetermined positions on an insulative substrate; and a step of forming a second resistor element having a predetermined pattern which electrically connects the first resistor elements, wherein an effective length of the second resistor element between the first resistor elements varies in accordance with a position of the second resistor element relative to the first resistor elements.
According to a third aspect of the invention, there is provided an electron gun assembly comprising a plurality of electrodes constituting an electron lens section for focusing or diverging electron beams, and a resistor for applying a resistor-divided voltage to at least one of the electrodes, wherein the resistor comprises: an insulative substrate; a plurality of first resistor elements disposed at predetermined positions on the insulative substrate; and a second resistor element having a predetermined pattern which electrically connects the first resistor elements, and wherein the resistor has a structure in which an effective length of the second resistor element between the first resistor elements varies in accordance with a position of the second resistor element relative to the first resistor elements.
According to a fourth aspect of the invention, there is provided a cathode-ray tube apparatus comprising: an electron gun assembly comprising a plurality of electrodes constituting an electron lens section for focusing or diverging electron beams, and a resistor for applying a resistor-divided voltage to at least one of the electrodes; and a deflection yoke for producing deflection magnetic fields for deflecting the electron beams emitted from the electron gun assembly, wherein the resistor comprises: an insulative substrate; a plurality of first resistor elements disposed at predetermined positions on the insulative substrate; and a second resistor element having a predetermined pattern which electrically connects the first resistor elements, and wherein the resistor has a structure in which an effective length of the second resistor element between the first resistor elements varies in accordance with a position of the second resistor element relative to the first resistor elements.
According to the above structures, the position of arrangement of the second resistor element is changed relative to the first resistor elements, whereby the effective wiring length of the second resistor element disposed between the first resistor elements is varied. Accordingly, the resistance value corresponding to the effective wiring length of the second resistor element can easily be varied. By adjusting the resistance value between the first resistor elements, the resistance division ratio can easily be altered and a predetermined necessary resistance division ratio can be obtained.
Thus, when a supply voltage needs to be varied in accordance with a change of specifications of the electron gun assembly, or when a resistance value needs to be adjusted in the process of manufacturing the resistor using screen printing, a predetermined resistance division ratio can easily be obtained without causing a decrease in manufacturing yield.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.